Implement items shifting, not quite working yet.

sugar/graphics/spreadlayout.py

@@ -26,8 +26,15 @@ _PLACE_TRIALS = 20
 _MAX_WEIGHT = 255
 _CELL_SIZE = 4
 
-class _Grid(object):
+class _Grid(gobject.GObject):
+    __gsignals__ = {
+        'child-changed' : (gobject.SIGNAL_RUN_FIRST,
+                           gobject.TYPE_NONE,
+                           ([gobject.TYPE_PYOBJECT]))
+    }
     def __init__(self, width, height):
+        gobject.GObject.__init__(self)
+
         self.width = width
         self.height = height
         self._children = []
@@ -74,8 +81,51 @@ class _Grid(object):
         self._children.append(child)
         self._add_weight(child.grid_rect)
 
+    def _move_child(self, child, new_rect):
+        child.grid_rect = new_rect
+        self.emit('child-changed', child)
+
+    def _shift_child(self, child):
+        rect = child.grid_rect
+        weight = self._compute_weight(rect)
+        new_rects = []
+
+        if (rect.x + rect.width < self.width - 1):
+            new_rects.append(gtk.gdk.Rectangle(rect.x + 1, rect.y,
+                                               rect.width, rect.height))
+
+        if (rect.x - 1 > 0):
+            new_rects.append(gtk.gdk.Rectangle(rect.x - 1, rect.y,
+                                               rect.width, rect.height))
+
+        if (rect.y + rect.height < self.height - 1):
+            new_rects.append(gtk.gdk.Rectangle(rect.x, rect.y + 1,
+                                               rect.width, rect.height))
+
+        if (rect.y - 1 > 0):
+            new_rects.append(gtk.gdk.Rectangle(rect.x, rect.y - 1,
+                                               rect.width, rect.height))
+
+        best_rect = None
+        for new_rect in new_rects:
+            new_weight = self._compute_weight(new_rect)
+            if new_weight < weight:
+                best_rect = new_rect
+                weight = new_weight
+        
+        if best_rect:
+            self._move_child(child, best_rect)
+
+        return weight
+            
+
     def _solve_collisions(self):
-        return False
+        for collision in self._collisions[:]:
+            weight = self._shift_child(collision)
+            if not weight:
+                self._collisions.remove(collision)
+
+        return (len(self._collisions) > 0)
 
     def _detect_collisions(self, child):
         for c in self._children:
@@ -122,6 +172,7 @@ class SpreadLayout(gobject.GObject,hippo.CanvasLayout):
         min_height, height = self.do_get_height_request(width)
 
         self._grid = _Grid(width / _CELL_SIZE, height / _CELL_SIZE)
+        self._grid.connect('child-changed', self._grid_child_changed_cb)
 
     def add_center(self, child):
         self._box.append(child)
@@ -170,3 +221,9 @@ class SpreadLayout(gobject.GObject,hippo.CanvasLayout):
         min_height, height = child.get_height_request(width)
 
         return int(width / _CELL_SIZE), int(height / _CELL_SIZE)
+
+    def _grid_child_changed_cb(self, grid, box_child):
+        # FIXME box_child->item is not exposed in the python bindings
+        for item in self._box.get_children():
+            if self._box.find_box_child(item) == box_child:
+                item.emit_request_changed()